Device for producing a pulsating flow of a fluid

ABSTRACT

Device for producing a pulsating flow of a fluid. The device comprises a vessel receiving the fluid and an inflatable bag within the vessel. The interior of the bag is connected to means for producing a pulsating gas flow including a gas valve controlled electrically by a pulse generator, the frequency and ratio between the work time and rest time of the generator being variable. The resulting pulsating fluid issues from the vessel by way of an outlet.

Elite States Patent 1 Kachelhoifer Sept. 11, 1973 BEVHCE FOR PRODUCING APULSATING FLOW OF A FLUID [75] inventor: Jean Kachelhotter,

Strasbourg-Cronenbourg, France [73] Assignee: Institut National De LaSante Et De La Recherche Medicale, Paris, France 22 Filed: Jan. 18,1972

I21] Appl. No.: 218,719

[30] Foreign Application Priority Data 417/384, 385, 557; 3/DIG. 2;128/DIG. 3, 1 D; 91/459, 460, 280; 137/13 {56] References Cited2,971,465 2/1961 Caillaud 417/383 X 3,123,007 3/1964 Orr .L 417/3832,033,210 3/1936 Tennant et al.... 417/383 3,658,443 4/1972 Fumagalli 1417/384 3,507,583 4/1970 James 417/385 X FOREIGN PATENTS OR APPLICATIONS221,685 11/1957 Australia 417/383 241,321 8/1960 Australia 417/394989,736 4/1965 Great Britain 417/384 Primary ExaminerCarlton R. CroyleAssistant ExaminerRichard Sher Att0rneylrvin S. Thompson et al.

[57] ABSTRACT Device for producing a pulsating flow of a fluid. Thedevice comprises a vessel receiving the fluid and an inflatable bagwithin the vessel. The interior of the bag is connected to means forproducing a pulsating gas flow including a gas valve controlledelectrically by a pulse generator, the frequency and ratio between thework time and rest time of the generator being variable.v The resultingpulsating fluid issues from the vessel by way UNITED STATES PATENTS ofan outlet- 2,87l,789 2/1959 Kiffer et a1 417/383 X 5 Claims, 3 DrawingFigures 14 1 l3 3 10 ll 15 9 l f e PATENTED SEP! I i973 SHEET 1 UF 2PATENTEB SEP] 1 I973 SHEET 2 UP 2 Fig.2B

DEVICE FOR PRODUCING A PULSATING FLOW OF A FLUID The present inventionrelates to a device for trans forming the continuous flow of a fluidinto a pulsating flow. More particularly, in a special application, theinvention relates to a device for obtaining in vitro a blood flow havingphysiological arterial characteristics.

At the present time, devices for perfusing organs isolated from theirnormal environment are employed more and more frequently inphysiological or experimental surgery laboratories. In conventionalperfusion devices in general use, the perfusion liquid is made to flowby a pump which is either peristaltic or has rollers and produces acontinuous flow. However, some perfusion devices having a pulsating flowexist. They employ mostly an alternating displacement of a pistonassociated with a pair of valves. Such devices are often expensive, lackflexibility as concerns the obtainment of desired pressure waveforms,and are not atraumatic when the perfusion liquid is constituted byblood.

An object of the invention is to remedy the drawbacks of devices of theconventional method'of perfusing organs, and to provide a simple methodfor obtaining within a fluid in motion or at rest pulses or pressureatmosphere through a tap 13. The valve 10 is convariations which areeither single, sequential or repetitive.

The invention provides a device for producing a pulsating flow of afluid, comprising a closed vessel which communicates with aconstant-flow pump connected to a source of fluid and with a load to besupplied with pulsated fluid, said vessel being adapted to containpermanently an amount of fluid, and a variable-volumepressure-modulating element located in the vessel and connected to apulse-producing source whereby it is possible to vary the volume of saidelement.

Owing to these features, the device according to the invention furnishesat its outlet a composite pressure wave including a constant componentand a variable modulating component which usually has a smalleramplitude than the constant component.

Preferably, the pressure modulating means is a small balloon orinflatable bag composed of elastically yieldable material and theimpulsive source comprisesa reservoir of a gas under pressure connectedto the bag through a valve.

Further features and advantages of the invention will be apparent fromthe ensuing description with reference to the accompanying drawings.

in the drawings FIG. 1 is a simplified diagram of a device forproducinga pulsating flow of liquid according to the invention, and

FIGS. 2A and 2B are diagrams comparing the pressures produced in thefemoral artery of a dog and in the arterial branch of .a dog intestinesegment undergoing extra corporal perfusion through the agency of adevice according to the invention (pressure expressed in millimetres ofmercury with respect to time).

In the embodiment shown in FIG. I, the device for producing a pulsatingflow of a fluid comprises a constant-flow pump 1, for example of thetype having rollers. This pump draws in, for example, perfusion liquidthrough a pipe 2 and discharges it continuously through a pipe 3connnected to a closed vessel 4 which is preferably cylindrical. Thevessel 4 is connected in its lower part to an outlet pipe 5 throughwhich the pulsating liquid flows to an organ which must be irrigated.The vessel 4 can be connected to the atmosphere through a tap 6 which isnormally closed and is provided to permit filling the vessel 4.

An element having a variable volume or modulator 7 is immersed in theliquid contained in the vessel 4. It is preferably in the form of asmall balloon or inflatable bag of elastically yiedable material (forexample rubber or elastic plastics material) which is secured to a pipe8 which is fixed with respect to the vessel 4.

A reservoir 9 of gas under pressure, such as nitrogen or air, isconnected to an electrically-operated valve 10 having three ways througha pressure-reducing valve and pressure gauge 1 1. An appropriate threeway valve is of the type sold by H.F.T., Paris, France, under n 5V-3-D.90,032 under licence of Skinner Electric Valve Division, U.S.A. Thevalve 10 is connected to the pipe 8 through a tap 12 and to a pipe 14leading to the trolled by an electric pulse generator 15, its pulsefrequency being adjustable, for example, between 3 and 300 per minuteand its mark-to-space ratio being settable as desired. Such generatorsare well known in the art and commerciallyiavailable so that nodescription need be made thereof here. For this purpose, the pulsegenerator n lV-lOOC-Electrona, manufactured and sold by Electrona,l3,rue J. Jaures 67380- Lingolsheim, France, is particularlyappropriate.

- The device according to the invention operates in the following mannerThe vessel 4 is filled either partly or completely by operating the pump1 and opening the tap 6 leading to the atmosphere, the pipe 5 beingtemporarily closed by a tap (not shown).

The gas circuit upstream of the valve 10 is put under gaseous pressurewhose value is chosen, bearing in mind the geometric and mechanicalcharacteristics of the vessel 4 and of the modulator 7, as a function ofthe amplitude of the pulsations it is desired to obtain.

The pulse frequency and the ratio between the work time (for examplesystolic time) and rest time (for example diastolic time) are set in thepulse generator 15 controlling the electrically operated valve 10 andcan be modified and adjusted at any time. In the absence" of the taps l2and 13 regulating the gaseous flows, the waveform of the pressures thenobtained in the outlet pipe 5 is that of two damped oscillatingmovements which follow each other. The first is positive with'respect tothe mean pressure and correspondsto the pressurizing of the modulator 7(opening of the valve'l0), whereas the second, which is negative,occurswhen the valve 10 is closed, which brings about simultaneously (it beinga'three-way valve) the opening of the dis-* charge circuit of thepressurizing gas. and therefore a sudden depressurization of themodulator '7.

Such a waveform is, usually of no interest and in particular notphysiological, but its configuration or shape can be corrected by aregulation of the gaseous supply and discharge flows .to which themodulator 7 is sub.- jected. Thus the partial and controlled closureofthe tap 12 stops the sudden-rise in pressure, avoids the appearance ofan oscillatory operation and permits suitably shaping the rising part(for example anacrotic) of the waveform. similarly, the shape of thedescending,

part (for example dicrotic) which starts at the start of thedepressurization is adjusted by regulating the discharge flow (tap 13),that is, the deflation of the modulator 7. The combination of these twopossibilities of adjustment enables a wide range of pressure profiles,and in particular physiological profiles, to be obtained. Measurementsand recordings of pressures have been carried out in the arterial branchof segments 30 centimetres long of the intestine of the dog undergoingextra-corporal perfusion. The pressure obtained at 1 cm from themesentery is practically identical in amplitude, frequency and profileto that measured in a femoral artery (see respectively FlGS. 2A and 2B).

The device according to the invention has in its very principle ofoperation an interesting property the mean pressure and the differentialpressure are independent. Indeed, for given mechanical characteristicsof materials constituting the vessel 4 and the modulator 7, theamplitude of the pulsations (pressure differential) is only a functionof the gaseous pressure supplied to the modulator. The mean pressure isdependent only on the resistance to flow of the downstream part of thecircuit and the continuous flow applied by the roller pump 1.Consequently, it is possible to obtain, within a wide range of flows, apulsatile operation having varied characteristics, and in particularphysiological characteristics, irrespective of the chosen mean pressureof flow.

With the device according to the invention it is possible a. To obtainflows having physiological pressure profiles. ln this field ofapplication it has high flexibility, related to the possibilities ofregulation of the gaseous pressurization and depressurization flows. Itis simple and can be easily adapted to any conventional apparatus forperfusion of isolated organs and even extracorporal circulationassemblies employed in cardiovascular surgery. In such apparatuses, theconversion of the continuous flow into a pulsatory flow can be effectedfor example in the region of the bubble remover which usually directlyprecedes the arterial branch of the perfusion circuit.

b. To obtain remote controls or relays. The device according to theinvention is of utility wherever a fluid (liquid or gas), which is atrest or flows, constitutes the support or vehicle for the transmissionof an information convertible into pulses or pressure variations.

Having now described my invention what [claim as new and desire tosecure by Letters Patent is l. A device for irrigating an element suchas a biological organ with a pulsating flow of a liquid comprising aclosed vessel having an inlet, a constant-flow pump connected to saidinlet and to a source of said liquid for supplying the latter into saidclosed vessel and for maintaining therein a substantially constantliquid level, said closed vessel further comprising an outlet connectedto said element, a variable-volume pressuremodulating element immersedin said liquid contained in the vessel, and means connected to saidpressuremodulating element for controlling the variations of the volumeof the latter.

2. A device for irrigating an element such as a biological organ with apulsating flow of a liquid comprising a closed vessel having an inlet, aconstant-flow pump connected to said inlet and to a source of saidliquid for supplying the latter into said closed vessel and formaintaining therein a substantially constant liquid level, said closedvessel further comprising an outlet connected to said element, a bag ofan elastically yieldable material in the liquid contained in the vessel,a reservoir containing a fluid under pressure, pipe means putting theoutlet of the reservoir in communication with the interior of the bagand pulsatory valve means inserted in said pipe means for producing apulsating flow of the fluid from the reservoir.

3. Adevice as claimed in claim 2, wherein the valve means is anelectrically operable valve means and said device further comprises agenerator of electric pulses connected to the valve means to controloperation of the valve means, the mark-to-space ratio of the generatorbeing variable.

4. A device as claimed in claim 2, wherein the valve means is a threeway valve capable of defining alternatively two fluid paths, one of saidpaths being connected in said pipe means between said bag and saidreservoir and the other paths being connected between said pipe meansand atmosphere, said device further comprising a first regulating valveconnected in said pipe means between said bag and said three way valveand a second regulating valve connected between said three way valve andatmosphere. v

5. A device as claimed in claim 2, further comprising a tap for puttingthe inside of the vessel in communication with the atmosphere when thevessel is being filled with fluid.

1. A device for irrigating an element such as a biological organ with apulsating flow of a liquid comprising a closed vessel having an inlet, aconstant-flow pump connected to said inlet and to a source of saidliquid for supplying the latter into said closed vessel and formaintaining therein a substantially constant liquid level, said closedvessel further comprising an outlet connected to said element, avariable-volume pressuremodulating element immersed in said liquidcontained in the vessel, and means connected to said pressuremodulatingelement for controlling the variations of the volume of the latter.
 2. Adevice for irrigating an element such as a biological organ with apulsating flow of a liquid comprising a closed vessel having an inlet, aconstant-flow pump connected to said inlet and to a source of saidliquid for supplying the latter into said closed vessel and formaintaining therein a substantially constant liquid level, said closedvessel further comprising an outlet connected to said element, a bag ofan elastically yieldable material in the liquid contained in the vessel,a reservoir containing a fluid under pressure, pipe means putting theoutlet of the reservoir in communication with the interior of the bagand pulsatory valve means inserted in said pipe means for producing apulsating flow of the fluid from the reservoir.
 3. A device as claimedin claim 2, wherein the valve means iS an electrically operable valvemeans and said device further comprises a generator of electric pulsesconnected to the valve means to control operation of the valve means,the mark-to-space ratio of the generator being variable.
 4. A device asclaimed in claim 2, wherein the valve means is a three way valve capableof defining alternatively two fluid paths, one of said paths beingconnected in said pipe means between said bag and said reservoir and theother paths being connected between said pipe means and atmosphere, saiddevice further comprising a first regulating valve connected in saidpipe means between said bag and said three way valve and a secondregulating valve connected between said three way valve and atmosphere.5. A device as claimed in claim 2, further comprising a tap for puttingthe inside of the vessel in communication with the atmosphere when thevessel is being filled with fluid.